Rolling or skidding platform ladder

ABSTRACT

A rolling or skidding platform ladder  1  is provided that has a platform ladder part  3  and an undercarriage part  5.  The undercarriage part  5  carries ground engaging parts  21  to enable rolling or skidding of the ladder  1.  The platform ladder part  3  has legs  7/9  which are raisable with the platform ladder part  3  to elevate the bottom of the legs  7/9  spaced from the ground when the platform ladder  1  is to be rolled or skidded. The undercarriage part  5  comprises a lever arm  29  that is pivoted thereto in a see-saw manner so as to extend generally parallel with the ground. One end of the lever arm  29  is for co-operating with the ladder part  3  to raise at least two legs of the ladder part  3  relative to the undercarriage part  5  so that the rolling ladder  1  can then be rolled or skidded without the at least two raised legs engaging the ground.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims the benefit of the filing dates of Australian application no. 2006905878 filed 23 Oct. 2006 and U.S. application No. 60/868589 filed 5 Dec. 2006, the contents of which are incorporated herein by reference in the entirety.

FIELD OF THE INVENTION

This invention relates to a rolling or skidding platform ladder (hereinafter referred to as “rolling ladder”), and relates particularly but not exclusively to a rolling ladder manufactured from aluminium.

BACKGROUND ART

Hitherto, rolling platform ladders have been known. One particular form of rolling platform ladder has a mechanism at the base of the ladder which allows the ladder part to be elevated relative to an undercarriage part so that the rolling ladder can be rolled or skidded on the undercarriage without the legs of the ladder impeding the general rolling or skidding movement. Such ladders have use in warehouses or other establishments where products are stored in racks or on high shelves. The known rolling ladder has a parallelogram arrangement for connecting the ladder part with the undercarriage part. Thus, in order to raise or lower the ladder part relative to the undercarriage part, the parallelogram swings to either extend or collapse. Thus, in turn, causes a corresponding raising or lowering of the ladder part. A clip arrangement is provided to hold the ladder part in the raised position. When the ladder is to be stood upon, the clip is unclipped so it releases its hold on the parallelogram arrangement, and the ladder moves downwardly so that the legs thereof engage with the ground. The mechanism is complicated and often subject to unintended collapsing operation when the platform ladder is pushed with extreme force in order to move the platform ladder.

OBJECT AND STATEMENTS OF THE INVENTION

There is a need for an alternative platform ladder.

Therefore, according to a first broad aspect of the present invention there is provided a rolling or skidding platform ladder (hereinafter referred as rolling ladder) comprising a platform ladder part and an undercarriage part, said undercarriage part carrying ground engaging parts to engaging with the ground during rolling or skidding of the rolling platform ladder,

said platform ladder part having legs for engaging with the ground when the ladder is to be climbed upon, said legs being raisable with the platform ladder part from the undercarriage part to elevate the bottom of the legs spaced from the ground when the platform ladder is to be rolled or skidded,

said undercarriage part comprising a lever arm pivoted thereto by a pivot in a see-saw manner so as to extend generally parallel with the ground, one end of the lever arm being for co-operating with the ladder part to raise at least two legs of the ladder part relative to the under carriage part when the opposite end of the lever arm is moved in a direction downwardly, so said rolling ladder can then be rolled or skidded without the at least two raised legs of the ladder part engaging the ground.

The raised legs of the ladder part can be moved to engage the ground by a person standing on the ladder part using their weight to cause the lever arm to swing and the opposite end of the lever arm to be raised by swinging in a direction upwardly.

The undercarriage part is generally of rectangular shape in plan view and is at a lowermost part of the ladder part, and extends between sides of the ladder part and front and rear legs of the ladder part, and directly above generally horizontally extending leg braces of the legs of the ladder part which are adjacent the ends of the legs of the ladder that engage the ground and which interconnect front and rear legs of the ladder part,

said undercarriage part carrying vertically downwardly extending pins fixed thereto which penetrate apertures associated with the leg braces, said pins carrying respective ground engaging wheels or skids at their ends closest to the ground.

The undercarriage part has the lever arm positioned generally midway between the two sides of the ladder part, and adjacent thereto a further lever arm pivoted to the undercarriage part by a further pivot, said pivot being at a front of the ladder part and said further pivot being at a rear of the ladder part, said further lever arm being also pivoted in a see-saw manner to said undercarriage part so as to extend generally parallel to the ground, one end of the further lever arm being for co-operating with the ladder part to raise the other two legs of the ladder part relative to the under carriage part when the opposite end of the further lever arm is moved in a direction downwardly.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention can be more clearly ascertained an example of an embodiment will now be described with reference to the accompanying drawings wherein:

FIG. 1 is a side, part isometric view of one example of rolling ladder in accordance with the present invention showing the rolling ladder in a collapsed position where a user can stand on the ladder part,

FIG. 2 is a view similar to that shown in FIG. 1 but showing the ladder part raised relative to an undercarriage part so as to enable the rolling ladder to either roll or skid,

FIG. 3 is a close up side elevational view taken along a sectional line that extends in a vertical plane slightly offset from the centre of the rolling ladder and in a direction from the front of the ladder towards the rear of the ladder, and showing the ladder part with the legs engaging the ground,

FIG. 4 is a view similar to that shown in FIG. 3 but showing the ladder part raised so that the legs do not touch the ground,

FIG. 5 is a close up view showing the undercarriage part elevated and raised relative to the ladder part so that the bottom of the legs are spaced from the ground,

FIG. 6 is a close-up underneath view of a foot engaging surface disposed proximate to treads of the ladder part.

FIG. 7 is a rear, part isometric view of the rolling ladder,

FIG. 8 is a plan view of the undercarriage part,

FIG. 9 is a close up side elevational view showing a slidable sheet like member that can be moved to overlie one or more treads of the ladder and act as a visual indicator that the ladder is closed for use, and

FIG. 10 is a front elevational view of the ladder showing how the sheet like member appears from the front of the ladder when the sheet like member is moved to overlie one or more of the treads of the ladder.

DETAILED DESCRIPTION OF EXAMPLE

Referring to all the figures generally, it can be seen that the rolling or skidding platform ladder 1 (hereinafter referred to as a “rolling ladder”), comprises a platform ladder part 3 and an undercarriage part 5. The ladder part 3 has front legs 7, rear legs 9, and leg braces 11. The leg braces 11 extend generally horizontally adjacent the ends of the legs 7, 9 that engage the ground. These braces 11 interconnect the front legs 7 with the rear legs 9 of the ladder part 3. The undercarriage part 5 has a generally rectangular configuration as shown in FIG. 7. The front legs 7 carry treads 13. An upper standing platform 15 is provided at the top of the rolling ladder 1. A pair of handrails 17 extend over an upper part of the rolling ladder 1 and over the standing platform 15. The lowermost parts of the legs 7 and 9 each have a respective foot thereon for engagement with the ground. FIG. 3 clearly shows each of the feet 19 engaged with the ground. The ladder part 1, is made from metal such as aluminium.

The undercarriage part 5 is made from elongate metal such as aluminium tube of rectangular transverse cross section and has ground engaging parts 21 for engaging with the ground during rolling or skidding of the rolling platform ladder. In this example, the ground engaging part 21 comprise four vertically downwardly extending steel pins 23 that penetrate respective apertures (not shown) in the leg braces 11. The pins 23 are best shown in FIGS. 3, 4 and 5. The apertures are not clearly shown in any of the figures but comprise bores drilled through the leg braces 11. Typically the pins 23 are of circular transverse cross sectional shape and pass through correspondingly circular shaped bores. Thus, the four pins 23 penetrate apertures provided in the leg braces 11 by way of being able to slide in those apertures/bores. The pins 23 are fixed relative to the undercarriage part 5 by upper and lower split pins 27. Whilst split pins 27 have been shown for fastening the pins 23 relative to the undercarriage part 5, other forms of fastening may be utilised such as welding, nut and bolt connections, or the like. The use of split pins 27 provides an economical form of fastening. The bores in the leg braces 11 may be provided with plastics material sliding bearing inserts 25 to permit for free sliding movement of the pins 23 as they penetrate the leg braces 11.

The undercarriage part 5 has a lever arm 29 pivoted thereto by a pivot pin 31 that passes through an upstanding post 33 at a forward end 35. The pivot pin 31 supports the lever arm 29 in a generally horizontally disposed condition and so the lever arm 29 can swing in a see-saw fashion about the pivot pin 31. FIGS. 3 and 4 show the arrangement best. One side of the lever arm 29 extends inwardly of the undercarriage part 5 whilst the other part of the lever arm 29 extends past the forward end 35 of the undercarriage part and underneath a tread 13 of the front legs 7 of the ladder part 3. The lever arm 29 therefore co-operates with the ladder part 3 by the other end of the lever arm 29 engaging, via a pressing bar 37, on the underside of a tread 13 near the bottom of the legs 7. This is clearly shown in FIG. 4 where the lever arm 29 is swung so that the pressing bar 37 is raised and the end of the lever 29 that extends inwardly of the undercarriage part 5 is pressed downwardly. In other words, the undercarriage part 5 comprises a lever arm 29 pivoted thereto by a pivot 31 in a see-saw manner so as to extend generally parallel with the ground and so one end of the lever arm co-operates with the ladder part 3 to raise at least two legs of the ladder part relative to the undercarriage part 5 when the opposite end of the lever arm 29 is moved in a direction downwardly. This permits the rolling ladder to be moved by being rolled or skidded without the at least two raised legs of the ladder part engaging the ground. A further lever arm 39 is pivoted to the other end 41 of the undercarriage part 5 by a pivot pin 43 passing through an upstanding post 45. The further lever arm 39 carries a pressing bar 47 which is used to engage with a transversely extending brace 49 so that downward swinging of the part of the further lever arm 39 that extends inwardly of the undercarriage part 5 moves the pressing bar 47 upwardly. The lever arm 29 and the further lever arm 39 are interconnected to each other by a common pivot 51 positioned midway between the front and the rear of the ladder part 3. This is best shown in FIG. 8. FIG. 8 also shows that each of the lever arm parts 29 and 39 are situated generally midway between the two sides of the ladder part 3. It can therefore be seen that the further lever arm 39 is for co-operating with the ladder part 3 to raise the other two legs (in this case the rear legs 9) relative to the undercarriage part 5 when the end of the further lever arm 39 that extends inwardly of the undercarriage part 5 is moved in a direction downwardly. Because the two lever arms 29 and 39 are interconnected by a common pivot 51, movement of one of the lever arms 29/39 causes the other lever arm 39 to move in a corresponding direction. Each of the lever arm 29 and further lever arm 39 carry foot engaging surfaces 53 in the form of plates attached to the respective lever arms 29/39. The foot engaging surfaces 53 are such that a user can place his foot within the ladder part 3 between the front legs 7 and the rear legs 9 from one side of the ladder part 3, and press either one of the foot engaging surfaces with his foot to cause both the lever arms 29 and 39 to move in a direction downwardly. A user can also place his foot between treads 13 to engage with the larger footprint foot engaging surface 23 to effect a similar operation of the lever arm 29.

FIG. 6 shows a close-up underneath view of the foot engaging surface 53 on lever arm 29. Here it can be seen that the foot engaging surface 53 extends to both the left and right hand sides of lever arm 29, whereas the smaller footprint foot engaging surface 53 on lever arm 39 extends only to one side. The larger footprint foot engaging surface 53 has a frame made from aluminium rectangular tube 67. The foot engaging surface 53 has a spacer 69 that spaces the under surface a distance upwardly of a sleeve tube 71 which, in turn, is slidably received over the end of arm 29. The spacer 69 and sleeve tube 71 are of aluminium and are welded to each other and to the under surface of the tube 67 as shown. The sleeve tube can then be fastened at the end of lever arm 29 by several bolts and nuts 73.

It should be noted that as the lever arms 29/39 move in a direction downwardly (as shown in FIG. 4), the lever arms 29 and 39 swing so that the ends pass each other. Because the larger footprint foot engaging surface 53 is spaced upwardly by spacer 69 the undersurface of the tube 67 (and the under surface of the foot engaging surface 53) does not interfere with the swinging of lever arms 29 and 39. During this movement, the front end 55 and the rear end 57 of the undercarriage part 5 are caused to bow outwardly. The dimension of spacing of the pivot pins 31, 43, and 51 are such that in order for the lever arms 29 and 39 to pass each other, the front end 55 and rear end 57 must bow outwardly. FIG. 8 clearly shows the arrangement where bowing has been exaggerated for illustrative purposes. This bowing causes flexing and the providing of a bias force to cause snap movement of the lever arms 29 and 39 as the lever arms 29 and 39 move to pass each other. The bias force is such that the ladder part 3 is maintained raised relative to the undercarriage part 5 so that the legs 7/9 are elevated from the ground. When a person steps onto a tread 13 of the ladder part 3, the person's weight will transfer through either pressing bar 37 or pressing 47 or both of the pressing bars 37/47 to apply a downward pressure to the respective ends of the lever arms 29/39 to cause the parts thereof that extend inwardly of the undercarriage part 5 to be raised upwardly. In other words, the ladder part 3 then moves downwardly relative to the undercarriage part 5 so that the legs 7, 9 can engage with the ground. Typically, the feet 19 provide a firm positioning of the respective legs 7 and 9. Accordingly, the weight of the person standing on a tread 13 is sufficient to cause movement of the ladder part 3 in this way.

It should be appreciated that the raising and/or lowering of the ladder part 3 is effected by operation of the lever arms 29/39 and/or by a person standing on the ladder part 3. This provides enhanced safety relative to the prior platform ladders where the undercarriage part is carried by a parallelogram mechanism and wherein the raising and/or lowering of the ladder part relative to the undercarriage part is effected by swinging of the parallelogram. In such cases, the mere pushing of the ladder can effect an unintended dislodgement of the ladder part being maintained in a position where the legs do not contact the ground.

FIGS. 9 and 10 clearly show a sheet like member 59 which is normally, in use, supported in a generally horizontal plane by generally horizontal extending guide rails 61 that are positioned under the standing platform and under the upper tread 13 of the ladder part 3. FIG. 8 shows the sheet like member 59 partly extended from the guide rails 61. The sheet like member 59 is made from sheet polyethylene and is provided with suitable indicia markings, as shown in FIG. 9, to indicate that the rolling ladder is closed for use. FIG. 9 shows the sheet like member 59 substantially fully extended from the guide rails 61 so that it hangs downwardly to overlie the treads 13 of the ladder part 3. The bulk of the sheet like member 59 is generally sufficient to inhibit unintended persons from lifting the sheet like member 59 and retracting it back into the guide rails 61. The sheet like member 59 has fingers 63 extending laterally outwardly from the side edges at the extreme front and rear ends thereof. These fingers are comprised by rods that are suitably fastened to the sheet like member 59 such as by clamping bolts (not shown). The fingers locate within channels in the guide 61 and permit for sliding and swinging action of a sheet like member 59 to occur. When the sheet like member 59 is fully retained within the guide rails 61, it extends in a generally horizontal plane and can be used as a shelf for storage of articles that may subsequently be required to be placed on shelves or the like to which the rolling ladder provides access to.

Modifications may be made to the invention as would be apparent to persons skilled in the art of producing rolling ladders or other sheet metal like products. For example, whilst the rolling ladder 1 has been described as being made from aluminium, it may be made from other metals such as mild steel. Aluminium is preferable because of its lightness. Whilst the lever arms 29/39 have been shown so that their free ends are within the confines of the front legs 7 and rear legs 9, it may be possible to cause them to extend across the front legs 7 and/or rear legs 9 so that a person may engage their foot therewith from either the front of the ladder, or the rear of the ladder. In addition, whilst the lever arms 29 and 39 are shown positioned generally midway between the left and right hand sides of the ladder, they may be positioned to one side or the other. Further, whilst the lever arms 29 and 39 are shown to engage with the ladder part by the use of pressing bars 37 and 47, there may be a physical link connection directly with the front legs 7 and the rear legs 9 such as by pins locating in arcuate shaped slots that generally follow the path of swinging of the ends of the lever arms 29 and 39 at the ends that engage with the ladder part. Further, the lever arms 29/39, may be suitably shaped and positioned to engage with the ladder part 3 directly without the use of the pressing bars 37/47. The pressing bars 37/47 however, distribute forces to the ladder part 3 over a greater surface area than if they were not provided.

In the examples shown, the ground engaging parts 21 are provided with castor wheels 65 to permit rolling movement of the platform ladder. Alternatively, the ground engaging part 21 may be provided with skid feet.

These and other modifications may be made without departing from the ambit of the invention the nature of which is to be determined from the foregoing description.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

In the claims which follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. 

1. A rolling or skidding platform ladder (hereinafter referred as rolling ladder) comprising a platform ladder part and an undercarriage part, said undercarriage part carrying ground engaging parts to engaging with the ground during rolling or skidding of the rolling platform ladder, said platform ladder part having legs for engaging with the ground when the ladder is to be climbed upon, said legs being raisable with the platform ladder part from the undercarriage part to elevate the bottom of the legs spaced from the ground when the platform ladder is to be rolled or skidded, said undercarriage part comprising a lever arm pivoted thereto by a pivot in a see-saw manner so as to extend generally parallel with the ground, one end of the lever arm being for co-operating with the ladder part to raise at least two legs of the ladder part relative to the under carriage part when the opposite end of the lever arm is moved in a direction downwardly, so said rolling ladder can then be rolled or skidded without the at least two raised legs of the ladder part engaging the ground.
 2. A rolling ladder as claimed in claim 1, wherein the raised legs of the ladder part can be moved to engage the ground by a person standing on the ladder part using their weight to cause the lever arm to swing and the opposite end of the lever arm to be raised by swinging in a direction upwardly.
 3. A rolling ladder as claimed in claim 1, wherein the undercarriage part is generally of rectangular shape in plan view and is at a lowermost part of the ladder part, and extends between sides of the ladder part and front and rear legs of the ladder part, and directly above generally horizontally extending leg braces of the legs of the ladder part which are adjacent the ends of the legs of the ladder that engage the ground and which interconnect front and rear legs of the ladder part, said undercarriage part carrying vertically downwardly extending pins fixed thereto which penetrate apertures associated with the leg braces, said pins carrying respective ground engaging wheels or skids at their ends closest to the ground.
 4. A rolling ladder as claimed in claim 1, wherein said undercarriage part has the lever arm positioned generally midway between the two sides of the ladder part, and adjacent thereto a further lever arm pivoted to the undercarriage part by a further pivot, said pivot being at a front of the ladder part and said further pivot being at a rear of the ladder part, said further lever arm being also pivoted in a see-saw manner to said undercarriage part so as to extend generally parallel to the ground, one end of the further lever arm being for co-operating with the ladder part to raise the other two legs of the ladder part relative to the under carriage part when the opposite end of the further lever arm is moved in a direction downwardly.
 5. A rolling ladder as claimed in claim 4, wherein the opposite ends of the lever arm and further lever arm, are interconnected by a common pivot, so when one is moved downwardly or upwardly, it will cause the other to move in a corresponding direction.
 6. A rolling ladder as claimed in claim 5, wherein the opposite ends of the lever arm and the further lever arm carry a person's foot engaging surface, said lever arm and said further lever arm being pivoted to each other generally midway between a front and a rear of the undercarriage part, whereby a user can place his foot within the ladder part between the front legs and rear legs and press either one of the foot engaging surfaces with his foot to cause both the lever arm and the further lever arm to move in a direction downwardly.
 7. A rolling ladder as claimed in claim 3, wherein there are four vertically downwardly extending pins, each being positioned on the undercarriage part to be adjacent a respective one of four legs of the ladder part, so that there will be a wheel or a skid adjacent each of the four legs.
 8. A rolling ladder as claimed in claim 6, wherein the lever arm and the further lever arm are pivoted to each other and to the front and rear of the undercarriage so that when the lever arms are moved to pass each other, during moving in a downward or upward direction, there will be a flexing of a front and a rear of the undercarriage part in a direction outwardly of the undercarriage part, said flexing providing a bias force to cause snap movement of the lever arm and further lever arm as the lever arm and further lever arm move to pass each other.
 9. A rolling ladder as claimed in claim 8 wherein the undercarriage part is fabricated from elongate metal.
 10. A rolling ladder as claimed in claim 1, wherein the ladder part carries a slidable sheet like member, said slidable sheet like member being supported in a generally horizontal plane by generally horizontal extending guide rails under the upper tread surface of the ladder part, and wherein the slidable sheet like member can slide along said rails so that one side thereof is positioned outwardly of the steps of the ladder, whereupon the one side can be swung downwardly to overlie one or more treads of the ladder and to act as a visual indicator that the rolling ladder is closed for use.
 11. A rolling ladder as claimed in claim 10, wherein the slidable sheet like member has fingers extending from side edges thereof, said fingers being received in a channel in the guide rails and being at both ends of the slidable sheet like member, and such that when the slidable sheet like member is slid so that the one side thereof is positioned outwardly, the fingers remaining in the channels will act like a hinge to allow the slidable sheet like member to swing thereabout to overlie the one or more treads. 